1,720,963 research outputs found
Partitioning forest evapotranspiration:interception evaporation and the impact of canopy structure, local and regional advection
No full textSpatial and temporal variation in interception evaporation, energy balance during rain and total water loss was explored in a structurally heterogeneous Norway spruce [Picea abies (L.) H. Karst.] plantation in western Denmark. The trees are arranged in a distinctive small scale mosaic (0.25 ha) of young open canopy stands interspaced with older mature closed canopy stands. The mature stands are bound by a single line of taller Grand Fir [Abies grandis] on their northern edge. Interception loss (I) was measured and modeled in the open and closed canopy stands and under a Grand Fir row using net precipitation gauges and the Gash rain interception model. Incorporating complementary data on individual stand transpiration, forest floor evaporation and total ET (Ringgaard et al., 2012) we show that (a) I is 3% points higher in the closed canopy than in the open canopy (34% and 31% of P-G respectively) while the Grand Fir row promotes a zone of relative drought with I = 47%, (b) in terms of total water loss, the open canopy has an annual ET of about 7.5% higher than the closed canopy stand and (c) in months with little precipitation there is good agreement between the individual components of the evaporation balance and the gap-filled eddy-covariance evapotranspiration (EC-ET) estimate while in months with high precipitation the EC-ET data underestimate both the magnitude and variability of I. The Gash model had to be parameterized separately for summer and winter. In winter, the available energy for evaporation during rain was dominated by regional scale advection of heat from the North Sea, while in summer half the available energy came from local advection. The mean evaporation rate during rain was 0.09 mm h(-1) in winter and 0.21 mm h(-1) in summer. (C) 2014 Elsevier B.V. All rights reserved.Villum foundatio
Partitioning of forest evapotranspiration:the impact of edge effects and canopy structure
No full textThe magnitude of small scale variability in tree transpiration was explored in a structurally heterogeneous Norway spruce (Picea abies (L.) H. Karst.) plantation in western Denmark. The trees are arranged in a distinctive small scale mosaic (0.25 ha) of young open-canopy stands interspaced with older mature closed-canopy stands. Tree transpiration was measured in the open and closed canopy stands using Granier type thermal dissipation probes; forest floor evapotranspiration (ET) was estimated by monitoring the weight of cut out sections of forest floor; and total ET was estimated using the eddy covariance (EC) method. We show that (a) canopy structure had a major impact on transpiration rate allowing the open-canopy stands to transpire at approximately 30% higher rate than the closed-canopy stands; (b) within the open-canopy stand there was a significant relation between tree size and sap-flux density; and (c) within the closed-canopy stands there was an edge effect with trees next to access roads and aisles being responsible for a disproportionately large part of the stand transpiration. Through careful scaling, taking into account the observed variability, it was possible to get good agreement on dry days between independent measures of transpiration plus forest floor ET and the EC estimate of total forest ET. On average transpiration and forest floor ET amounted to 86% of the EC estimate on dry days. (c) 2012 Elsevier B.V. All rights reserved.Villum foundatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
On variability of evapotranspiration:the role of surface type and vegetation
No full textThis dissertation is part of the long-term catchment-scale hydrological observatory, HOBE, situated in the Skjern River catchment covering 2500 km2 on the western coast of Denmark. To gain a more detailed knowledge of how evapotranspiration is controlled by the local surface and weather patterns, eddy-covariance systems was installed over the tree dominant surface types in the catchment; an agricultural field, a spruce [Picea abies (L.) H. Karst] plantation and a meadow site. Measurements started in late 2008, and the full evaporation and energy balances for the years 2009-2011 forms the basis for this study. At the spruce plantation additional separate measurements of transpiration, interception evaporation and forest floor evaporation was performed. Transpiration was measured in the growing season of 2010 using Granier type TDP sap flux probes, interception was measured using net precipitation gauges for the years of 2010 and 2011 and forest floor evaporation was measured on a campaign basis by weighing cut out sections for forest floor. The cumulative measured evapotranspiration from the three surfaces showed large differences. 2009 was an unusually dry year with much lower than normal rates of precipitation in April, May and June, while 2010 and 2011 where normal years in terms of precipitation. The meadow site and agricultural site had the largest evapotranspiration in dry year of 2009 at 512 and 470 mm respectively, while the normal years 2010 and 2011 saw 446 and 455 mm for the meadow and 406 and 400 mm for the agricultural site. The spruce plantation showed the opposite pattern. In 2009 the ET was 494 mm while in 2010 and 2011 the sum was 545 and 544 mm respectively. In all years the agricultural site had less evapotranspiration than the natural surfaces. In the dry year 2009 the meadow had slightly more evapotranspiration than spruce plantation, while in the normal years 2010 and 2011 the forest had considerably more evapotranspiration than either the Meadows or the Farm. At the agricultural site, transpiration was the most important component of the evapotranspiration. The rate of evapotranspiration was controlled by crop development and by the available energy. At the meadow site soil evaporation and evaporation from free water surfaces was the most important parts of the evapotranspiration. The rate of evapotranspiration was controlled by the water level in the Skjern River which influenced the ground water level in the meadows and by the available energy. At the spruce plantation transpiration and terception evaporation were both important. The rate of transpiration was heavily influenced by stomatal control in response to high vapor pressure deficits. In addition soil moisture stress had a limiting effect during prolonged dry periods. Interception evaporation was controlled by the amount and duration of precipitation. During rain, advection was found to comprise about half the energy balance of the spruce plantation in summer and the majority the energy balance in winter. On average, 19% of the precipitation evaporated during rain in summer, and 12% of the precipitation evaporated during rain in winter. Canopy structure in the forest were found to affect both transpiration and interception evaporation. Young stands with an open canopy structure transpired at about 30% higher rate than mature stands with a close canopy structure; the young stands had an interception evaporation of 31% of the gross precipitation, while the mature stands had an interception evaporation of 34% of the gross precipitation. Within the mature stands there was an edge effect with trees next to access roads and aisles being responsible for a disproportionally large part of the stand transpiration
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
